1. Field of the Invention
The present invention relates to new immunological adjuvants, more particularly derivatives of hydrosoluble extracts of mycobacteria, and to a process for their production. The invention also relates to pharmaceutical compositions containing said derivatives obtained from hydrosoluble extracts of mycobacteria.
2. Description of the Prior Art
It is known that the hydrosoluble part of "D waxes" of mycobacteria, currently named "Poly PA" possess adjuvant activity. Methods have already been described for the extraction of this hydrosoluble part of mycobacteria, notably by chemical processing, by enzymatic processing or by homogenization or acetylation.
In Belgian Patent No. 801,016 there are described hydrosoluble extracts of mycobacteria whose molecular weight is comprised between 3,500 and 30,000. They possess a non-arthrogenic adjuvant activity when they are added to a mineral oil (Freund's incomplete adjuvant).
These hydrosoluble extracts are constituted essentially from a mixture in variable proportions of hydrosoluble fragments of the cell wall, possibly associated with non-amino reducing sugars. The hydrosoluble fragments of the cell wall are constituted essentially by a tetrasaccharide-heptapeptide and by its dimer, trimer and tetramer.
The tetrasaccharide-heptapeptide of the cell wall has the following molecular composition: N-acetylglucosamine (2), N-acetylmuramic acid (2), alanine (3), glutamic acid (2), .alpha.,.alpha.'-diaminopimelic acid (2), and its skeleton can be represented by the following diagram: ##STR2## NAG: N-acetylglucosamine NAM: N-acetylmuramic acid
Ala: alanine
Glu: glutamic acid
Dap: .alpha.,.alpha.'-diaminopimelic acid
Between two NAG-NAM units, it is possible to have, either the presence of a covalent linkage, or the total absence of a linkage; in the latter case, the linkage of the whole is ensured by the peptide portion.